Ground Motion Model for Puget Sound Cohesionless Soil Sites

Abstract

Surface response spectra for earthquake events must be based upon proper input seismic modelling. The surface response spectrum can be determined by convoluting a base response spectrum with a spectral amplification for the site. This required that an appropriate base spectrum of the earthquake motion and soil response model must have been used to develop the surface response spectra. Earthquakes in the Puget Sound basin are generally deep focus subduction zone events. These earthquakes are significantly different than the shallow focus strike slip events of California which are commonly used for this purpose. The spectral site amplification must be determined for the soils of the region. This paper considers the cohesionless soil sites only. The computer program SHAKE was used to evaluate the spectral amplification of different sites. Parameters for SHAKE were determined from Standard Penetration Test data. Parametric sensitivity studies were conducted for the spectral site amplification.